Today, passive radio-frequency identification (RFID) tags are widely used for real-time location systems (RTLS) in tracking goods, assets and people. An RTLS typically outputs the location of each sensor or RFID tag with three coordinates relative to a fixed known position of the RFID/sensor reader.
In a fixed reader infrastructure in indoor environments such as warehouses, distribution centers, or retail stores, the coordinates of each reader, excitation node and associated antennas are typically manually measured and individually input to the system by a human operator when initially configuring the system. RFID systems can also include mobile RFID readers. Mobile RFID readers can be handheld units operated by humans, robots, or drones equipped with an embedded RFID reader. In mobile applications, the position of the reader varies when the reader is moved for the purpose of covering different regions in a physical area.